Process Capability

Process capability is a rating that describes the ability of a process to perform as expected. Often referred to as C_pk, this tells how well a process can be performed and delivered defect free results. The C_pk is compared to ‘1.00’ as a measure of how ‘good’ a process is in performing to expectation.

• A C_pk < 1.00 indicates a process with variation that exceeds a specified expected performance window.
• A C_pk = 1.00 indicates that 99.9% performance falls within a specified expected performance window.
• A C_pk > 1.00 indicates a process with tight variation around its mean. It performs consistently better than a specified expected performance window.

A process with a C_pk = 2.00 is equivalent to a Six Sigma level performance, or 3.4 defective parts per million parts.